2.78b : Blender system Cloud texture addon not showing
The Blender ID add-on was first bundled with Blender in 2.78; it was included with the Blender Cloud add-on to allow people with Blender 2.77 to use it too.

To get to the Texture Browser, the easiest way is to press CTRL+ALT+SHIFT+A. Alternatively, in the UV/Image editor, choose 'Image' > 'Get Image from Blender Cloud'. 

The documentation is available from the add-on screen itself, and describes some of the other features too (like Blender Sync):